Toshiba has developed a prototype direct methanol fuel cell (DMFC) that it says will end the need for rechargeable batteries on notebooks.

Toshiba, which developed the hard drive used by Apple in its iPod, claims its new fuel cell has an average output of 12 watts and a maximum output of 20 watts. It gives about 5 hours of operation with 50 millilitres of fuel, Toshiba said, and runs on replaceable methanol cartridges.

Methanol in a fuel cell delivers power most efficiently when it is mixed with water in a 3 to 6 per cent concentration. This has made the fuel tank too large for portable equipment until now, Toshiba said. However, the new cell includes a system whereby the methanol is diluted by water produced in the power generation process. This process allows the methanol be stored at a higher concentration, allowing the fuel tank to shrink to a tenth of the size previously required.

The computer communicates with the fuel cell, giving information on its operating status, so that the fuel cell can balance power demand and supply. Sensors in the cell monitor methanol concentration and tell users when to change the cartridge, Toshiba said.

The fuel cell can be directly connected to a computer or other portable device in place of a lithium-ion battery, Toshiba said.

Two cartridge sizes have been developed: a 120 gram, 100 millilitre cartridge offering ten hours of operating time, and a 72 gram, 50 millilitre version giving five hours of operation. The fuel cell itself weighs 900 grams, Toshiba said.

The DMFCs are expected to be available f in 2004, the Toshiba said.